(That’s in Arch, by the way. But I think the xscreensavers should be in the same place in Ubuntu too. Other shades of Linux probably can do that too, maybe with a little path adjustment.) I used the ncolors flag because otherwise the colors seem to fade too fast, and it doesn’t have a retro effect.

There are other flags too; experiment with colors and shades and see what you come up with.

in KDE one can do that with the KDE background.
right click on Desktop -> Desktop Settings -> Background -> Advanced
Then use “Use this program to draw background” and enter the command above.
It works partly – until the normal screen saver kicks in or you logged out or you went to standby – don’t know how to reactivate it again.
And you don’t see your desktop icons…

I’ve tried to use this method with cairo-compmgr, but it isn’t working. When composite is on, cairo-compmgr shows solid filled screen, i don’t know if it’s another, non-root window, or it’s some problem with sharing gl subsytem or something else

Good question. To be honest, I don’t think I ever used them in conjunction, but my experience with xcompmgr and xscreensaver against the root window suggests it might not be something they’re prepared for. In any case, if you get it working, let me know.